The present invention relates to a digital video receiving apparatus for receiving a digital video signal in relation to a digital TV, a digital CATV and a digital broadcasting device.
FIG. 14 shows a multimedia information processing apparatus disclosed in xe2x80x9ca codec having broadcasting quality for satellite communicationxe2x80x9d, Hattori, Tanaka, Asano, Asai and Sakado, Mitsubishi Denki Technical Gazette, Vol. 67, No. 7, pp. 33-38 (1993).
A conventional digital video receiving apparatus is explained using FIG. 13 and FIG. 14. FIG. 13 shows an example of a signal frequency layout on a satellite transponder having a two-wave transmission mode. In FIG. 13, a high picture quality mode means a mode for transmitting two-waves on a transponder and a higher quality video and audio. SNG (Satellite News Gathering) multiplex mode means a mode for multiplexing two programs of SNG mode, which can transmit four waves in maximum via a transponder of a communication satellite xe2x80x9cSuper Birdxe2x80x9d, and for transmitting two video programs via one wave. In FIG. 13, the two-waves are multiplexed and each wave multiplexes two programs.
When the two-waves shown in FIG. 13 are demultiplexed and received simultaneously, four program digital video receiving apparatuses 400 (two apparatusesxc3x97two programs) (shown in FIG. 14) are necessary. In the high picture quality mode, one wave carries one program, but in the SNG multiplex mode two programs are carried in one wave as shown in FIG. 14. The decoding operation of the SNG multiplex mode is explained below.
In FIG. 14, a down converter 402 selects any one of SNG multiplexed waves 511 or 512 in FIG. 13 from a received IF (Intermediate Frequency) signal 401. QPSK demodulator 403 digitally demodulates the selected wave. A Viterbi decoder 404 corrects errors and a 2CH demultiplexer 410 demultiplexes a wave signal into two programs. One of the program signals is corrected through a de-interleave portion 411, a Reed-Solomon decoder 412 and a de-scramble portion 413 and outputted to a demulitplexer 430.
The other program signal is demultiplexed by the 2CH demultiplexer 410 into a digital video output 422, which is inputted into the 2CH demultiplexer 410 of the other program digital video receiving apparatus 400 as a digital video output 421. The output signal from the 2CH demultiplexer 410 of the other program digital video receiving apparatus 400 is also corrected through the circuits 411, 412 and 413 and outputted to the demultiplexer 430 in the same manner as described above.
Conventionally, one SNG multiplexed wave includes two programs. The respective SNG multiplexed wave is demultiplexed into one program by the 2CH demultiplexer 410 and outputted to the demultiplexer 430. A video decoder 432 receives a VBI (vertical blanking line interval) signal 431 from the demultiplexer 430 and outputs a video signal 441 to a terminal. An audio decoder 433 decodes an audio coded signal received from the demultiplexer 430 to output an audio signal 422. Similarly, an order-wire-interface 434 outputs a communication signal 443 and a data-interface 435 outputs a terminal data signal 444.
Conventionally, only digitally coded programs can be received. Therefore, an analog video picture and a digital video picture cannot be received by the same receiving terminal apparatus.
A conventional digital video receiving terminal apparatus only can receive one digital video program, but it cannot display a multi-channel digital video picture.
Also, the conventional digital video receiving terminal apparatus cannot display respective different digital video pictures on a plurality of terminals (monitors).
A data demultiplexer of the conventional digital video receiving terminal apparatus can only demultiplex data accompanied with one program, but it cannot demultiplex data corresponding to a plurality of digital video programs.
For example, when the computing quantity for decoding HDTV (High Definition Television) of a high picture quality digital TV is six times as much as that for SDTV (Standard Definition Television) of a normal digital TV, a data decoder of the conventional digital video receiving terminal apparatus can decode one HDTV picture or one SDTV picture, but it cannot decode a plurality of SDTV pictures, simultaneously, or a plurality of SDTV pictures plus one HDTV picture, simultaneously.
It is an object of the present invention to be able to see different programs independently on a plurality of monitors using one digital video receiving apparatus.
It is another object of the present invention to be able to see one HDTV program as well as a plurality of SDTV programs at the same time on a monitor using one digital video receiving apparatus.
It is a further object of the present invention to be able to see digital TV programs sent by digital signal as well as analog TV programs sent by analog signal at the same time on a monitor using one digital video receiving apparatus.
According to one aspect of the invention, a digital video receiving apparatus receives digital broadcasting programs including a plurality of multiplexed media such as video, audio and data, and provides the programs to subscribers. The apparatus includes a tuner for receiving a multiplexed signal and converting it to a digital base band signal and a demodulator for decoding the digital base band signal provided from the tuner. The apparatus further includes a demultiplexer for selecting one or more programs from the multiplexed programs including a plurality of media such as a video signal, an audio signal and a data signal according to a program selection signal provided from outside, and for demultiplexing respective bit streams including a video signal, an audio signal or a data signal. The apparatus further includes a video decoder for decoding the video signal demultiplexed by the demultiplexer, an audio decoder for decoding the audio signal demultiplexed by the demultiplexer, and a data decoder for decoding the data signal demultiplexed by the demultiplexer.
According to another aspect of the invention, the video decoder in the digital video receiving apparatus includes a bit stream divider and a plurality of video decoding units, each of the video decoding units including a partial video decoder and a memory. The bit stream divider generates video streams including a video signal, an audio signal and a data signal for each channel, using a clock and a stream identification signal. Each video decoding unit decodes the respective video stream for each channel using the partial video decoder and the memory, and outputs the decoded signal as a video output signal.
According to a further aspect of the invention, the digital video receiving apparatus further includes a channel demultiplexer for generating a video stream, a clock signal and a stream identification signal for each channel, using a bit stream including a video signal, an audio signal and a data signal, a clock signal and a stream identification signal each of which is outputted from the demultiplexer. The video decoder, the audio decoder and the data decoder process the respective signals for each channel, decode and output the video signal, the audio signal and the data signal for each program.
According to a still further aspect of the invention, the video decoder in the digital video receiving apparatus includes a plurality of video decoding units, each of the video decoding units including a partial video decoder and a memory. Each video decoding unit decodes the bit stream including a video signal, an audio signal and a data signal outputted from the channel demultiplexer, using a clock signal and a stream identification signal, and outputs a decoded signal as a video output signal.
According to a further aspect of the invention, a digital video receiving apparatus receives digital broadcasting programs including a plurality of multiplexed media such as a video, audio and data, and provides the programs to subscribers. The digital video receiving apparatus includes a tuner for receiving a multiplexed signal and converting it to a digital base band signal and a demodulator for decoding the digital base band signal provided from the tuner. The digital video receiving apparatus further includes a demultiplexer for demultiplexing and outputting a bit stream including a video signal, an audio signal and a data signal, a clock and a stream identification signal for each channel according to a selection signal, when a multiplexed signal is SDTV, and for demultiplexing and outputting a bit stream including a video signal, an audio signal and a data signal, a clock and a stream identification signal for each partial picture according to a selection signal, when the multiplexed signal is HDTV. The digital video receiving apparatus further includes a video decoder for decoding the video signal demultiplexed by the demultiplexer, an audio decoder for decoding the audio signal demultiplexed by the demultiplexer, a data decoder for decoding the data signal demultiplexed by the demultiplexer, a display synthesizer for synthesizing a plurality of the signals outputted from the video decoder and generating a video signal to display it on one monitor, an audio selector for selecting one of the audio signals outputted from the audio decoder, and a data selector for selecting one of the data signals outputted from the data decoder.
According to a further aspect of the invention, the video decoder in the digital video receiving apparatus includes a bit stream divider and a plurality of video decoding units, each of the video decoding units including a partial video decoder and a memory. The bit stream divider generates video streams for each channel from the video signal outputted from the demultiplexer, according to the switching signal and each of the video decoding units decodes the video stream for each channel to output a video signal, when the multiplexed signal is SDTV. The bit stream divider further generates video streams for each partial picture from the video signal outputted from the demultiplexer, according to the switching signal and each of the video decoding units decodes the video stream for each partial picture to output a video signal, when the multiplexed signal is HDTV.
According to a further aspect of the invention, the display synthesizer in the digital video receiving apparatus includes a plurality of enlarger/reducer units and a screen overlay unit. The display synthesizer enlarges or reduces sizes of the decoded signals inputted from the video decoder, superposes a plurality of the enlarged or reduced video signals and generates a video signal to display on one monitor in the case of SDTV.
According to a further aspect of the invention, the digital video receiving apparatus further includes an NTSC/PAL decoder. The tuner branches a received multiplexed signal to an analog base band signal and a digital base band signal. The NTSC/PAL decoder decodes the analog base band signal provided from the tuner to generate a decoding video signal. The display synthesizer synthesizes the analog video signal from the NTSC/PAL decoder and the digital video signal from the video decoder, and generates a video signal to display the analog video signal and the digital video signal on one monitor.
According to a further aspect of the invention, the display synthesizer in the digital video receiving apparatus includes a screen regenerator and a screen overlay unit. When no analog TV signal is inputted from the NTSC/PAL decoder, the display synthesizer synthesizes the digital HDTV video signal received from the video decoder to generate a video signal to display on one monitor. When the analog TV signal is inputted from the NTSC/PAL decoder, the screen overlay unit superposes the HDTV video signal and the analog TV signal and generates a video signal to display on one monitor.